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Gemooy.md

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Gemooy

This document aims to describe Gemooy, an esoteric programming language.

Program structure

A Gemooy program consists of an unbounded two-dimensional grid of cells; each cell may contain one of three symbols: @, #, or blank. A program text may contain any other symbols, but they are treated as blank cells upon program load. The symbols $ and % have special meaning; $ indicates the initial position of the instruction pointer, % indicates the initial position of the data pointer. All cells outside of the loaded program are considered to contain blanks.

Program state

Pointing into the grid is an instruction pointer. The instruction pointer is at any time moving in one of eight directions corresponding to the deltas (dx, dy) where -1 <= dx <= 1 and -1 <= dy <= 1 and not (dx = 0 and dy = 0). The instruction pointer is initially travelling southeast (dx = 1, dy = 1).

Also pointing into the grid is a data pointer. The cell under the data pointer can be "incremented", which means:

  • If it is a blank, it becomes a #.
  • If it is a #, it becomes a @.
  • If it is a @, it becomes a blank.

Decrementation is the inverse operation.

Program execution

The cells that the instruction pointer passes over are executed. Executing @ causes the direction of the instruction pointer's travel to turn 45 degrees clockwise if the cell at the data pointer contains a blank, 45 degrees counterclockwise if the cell at the data pointer contains #, or not at all if the cell at the data pointer contains @.

Executing # has an effect that depends on direction that the instruction pointer is travelling:

  • North = Move data pointer one cell north, skip instruction pointer over next cell.
  • East = Move data pointer one cell east, skip instruction pointer over next cell.
  • South = Move data pointer one cell south, skip instruction pointer over next cell.
  • West = Move data pointer one cell west, skip instruction pointer over next cell.
  • Northeast or Northwest = Increment cell at data pointer.
  • Southeast or Southwest = Decrement cell at data pointer.

Executing a blank does nothing.

The program terminates when the instruction pointer travels out of bounds, i.e. away from the populated grid and into empty space from which it cannot possibly return.